1. Field of the Invention
This invention relates generally to a ferroelectric memory and method for manufacturing same and, more particularly, to a ferroelectric memory with a structure formed, on an insulation film, with a lower electrode, a ferroelectric and an upper electrode in this order, and a method for manufacturing such a ferroelectric memory.
2. Description of the Prior Art
The conventional ferroelectric memory 1 of this kind, shown in FIG. 13, includes a not-shown semiconductor substrate and a first insulation film 2 formed thereon. On the first insulation film 2, a lower electrode 3, a ferroelectric film 4 and an upper electrode 5 are formed in this order. Further, a second insulation film 6 is formed in a manner covering these films. To fabricate a ferroelectric memory 1, a conductive film 3a is formed of platinum (Pt) or the like by sputtering over the first insulation film 2 formed on the semiconductor substrate, as shown in FIG. 14(A). Then, a ferroelectric film 4a is formed of lead zirconate titanate (PZT) or the like on the conductive film 3a by a sol-gel process. A conductive film 5a is further formed by sputtering platinum (Pt) or the like over the ferroelectric film 4a. Then, as shown in FIG. 14(B) dry etching is conducted sequentially on the conductive film 5a, the ferroelectric film 4a and the conductive film 3a, thereby providing an upper electrode 5, a ferroelectric film 4 and a lower electrode 3. Thereafter, an insulation film (FIG. 13) is formed in a manner covering these films by a CVD process.
In the prior art, however, a conductive film 5a, a ferroelectric film 4a and a conductive film 3a are formed to a thickness to provide an upper electrode 5, a ferroelectric film 4 and a lower electrode 3, so that dry etching is then conducted throughout a total film thickness in order to remove unwanted portions of these films. Thus, the prior art has required a much greater etch amount and hence a longer etch time. This results in longer exposure of the ferroelectric film 4 to the plasma atmosphere during a dry etch process. The plasma however has effects upon the ferroelectric 4 that lower its switching charge amount (Qsw). Thus, there has been a fear of causing such problems as worsening the symmetry in hysteresis and deteriorating the characteristics of coerciveness and fatigue.